Improved KASUMI block cipher for GSM-based mobile networks

Abstract

ABSTRACT KASUMI is an eight-round Feistel network that produces 64-bit output from 64-bit input by using 128-bit key. Three functions FL, FO and FI are involved in each round and each function has its respective keys KL, KO and KI . In this work, modifications in the existing KASUMI are proposed to reduce the encryption time. In proposed KASUMI, the single FL function is divided into two functions such as FLleft and FLright. The FLleft function is constructed with two Rijndael’s 32-bit S -boxes. The FLright function is constructed with four stages where third and fourth stages are performing XOR and shift operations before final concatenation of two 16-bit data of FL function. The simulation results are provided in terms of encryption time taken versus number of iteration and encryption speed versus number of iteration to show that the proposed KASUMI block cipher design outperforms the conventional KASUMI block cipher.